全文获取类型
| 收费全文 | 136篇 |
| 免费 | 7篇 |
| 国内免费 | 2篇 |
专业分类
| 测绘学 | 4篇 |
| 大气科学 | 9篇 |
| 地球物理 | 36篇 |
| 地质学 | 41篇 |
| 海洋学 | 17篇 |
| 天文学 | 27篇 |
| 自然地理 | 11篇 |
出版年
| 2024年 | 1篇 |
| 2023年 | 1篇 |
| 2022年 | 1篇 |
| 2021年 | 5篇 |
| 2020年 | 2篇 |
| 2019年 | 2篇 |
| 2018年 | 8篇 |
| 2017年 | 6篇 |
| 2016年 | 5篇 |
| 2015年 | 5篇 |
| 2014年 | 4篇 |
| 2013年 | 9篇 |
| 2012年 | 3篇 |
| 2011年 | 5篇 |
| 2010年 | 8篇 |
| 2009年 | 12篇 |
| 2008年 | 8篇 |
| 2007年 | 6篇 |
| 2006年 | 8篇 |
| 2005年 | 8篇 |
| 2004年 | 2篇 |
| 2003年 | 9篇 |
| 2002年 | 1篇 |
| 2001年 | 3篇 |
| 2000年 | 7篇 |
| 1999年 | 4篇 |
| 1998年 | 5篇 |
| 1997年 | 2篇 |
| 1996年 | 1篇 |
| 1995年 | 1篇 |
| 1992年 | 2篇 |
| 1990年 | 1篇 |
排序方式： 共有145条查询结果，搜索用时 15 毫秒
1.
2.
3.
4.
Tiziana Tuvè Antonio Teramo Jesus Ibañez Carla Bottari Domenica Termini 《Pure and Applied Geophysics》2005,162(4):747-760
A modelling of the observed macroseismic intensity of historical and instrumental earthquakes in southern Spain is proposed, with the aim of determining the macroseismic parameters for seismic hazard evaluation in a region in which the characterization of intensity distribution of seismic events shows different levels of difficulty referable to the complex faults system of the area in study. The adopted procedure allows an analytical determination of epicenters and principal attenuation directions of earthquakes with a double level of verification with reference to the maximum shaking area and structural lineaments of the region, respectively. The analyses, carried out on a suitable number of events, highlight, therefore, some elements for a preliminary characterization of a seismic zonation on the basis of the consistency between seismic intensity distribution of earthquakes and corresponding structural framework. 相似文献
5.
Aude?ValadeEmail authorView author&#;s OrcID profile Sebastiaan?Luyssaert Patrick?Vallet Sylvestre?Njakou Djomo Ingride?Jesus Van Der Kellen Valentin?Bellassen 《Carbon balance and management》2018,13(1):26
Background
Concern about climate change has motivated France to reduce its reliance on fossil fuel by setting targets for increased biomass-based renewable energy production. This study quantifies the carbon costs and benefits for the French forestry sector in meeting these targets. A forest growth and harvest simulator was developed for French forests using recent forest inventory data, and the wood-use chain was reconstructed from national wood product statistics. We then projected wood production, bioenergy production, and carbon balance for three realistic intensification scenarios and a business-as-usual scenario. These intensification scenarios targeted either overstocked, harvest-delayed or currently actively managed stands.Results
All three intensification strategies produced 11.6–12.4 million tonnes of oil equivalent per year of wood-based energy by 2026, which corresponds to the target assigned to French wood-energy to meet the EU 2020 renewable energy target. Sustaining this level past 2026 will be challenging, let alone further increasing it. Although energy production targets can be reached, the management intensification required will degrade the near-term carbon balance of the forestry sector, compared to continuing present-day management. Even for the best-performing intensification strategy, i.e., reducing the harvest diameter of actively managed stands, the carbon benefits would only become apparent after 2040. The carbon balance of a strategy putting abandoned forests back into production would only break even by 2055; the carbon balance from increasing thinning in managed but untended stands would not break even within the studied time periods, i.e. 2015–2045 and 2046–2100. Owing to the temporal dynamics in the components of the carbon balance, i.e., the biomass stock in the forest, the carbon stock in wood products, and substitution benefits, the merit order of the examined strategies varies over time.Conclusions
No single solution was found to improve the carbon balance of the forestry sector by 2040 in a way that also met energy targets. We therefore searched for the intensification scenario that produces energy at the lowest carbon cost. Reducing rotation time of actively managed stands is slightly more efficient than targeting harvest-delayed stands, but in both cases, each unit of energy produced has a carbon cost that only turns into a benefit between 2060 and 2080.6.
We examined the abundance and distribution of Eleodes extricata (Tenebrionidae) in a semi-arid region of West Texas. During the 2-year study, climatic conditions were extreme but opposite, with 1997 being unusually wet and mild, and 1998 being unusually dry and hot. These conditions were associated with striking differences in the population structure of the beetles. Under identical pitfall-sampling efforts, we captured 1562 and 671 individuals in 1997 and 1998, respectively. Capture rates were lowest in grassland, and highest in sand shinnery oak, and within the latter, they were lowest in blowouts, intermediate along the edges of blowouts, and highest under vegetative cover. Sex ratios were consistently female-biased, and the degree of bias increased from spring through fall in both years. These increases were more pronounced in 1998, with the sex ratios of early and late sampling periods differing by over four-fold, from 1·15 to 5·00. Females were heavier than males, and the dry masses of both sexes increased from spring though fall in both years. As with sex ratios, these increases were more pronounced in 1998. Only the largest beetles survived the drought, illustrating how extreme conditions can exert especially strong directional selection, and affect sex ratios in populations with sexual size dimorphism. 相似文献
7.
Conditioning mean steady state flow on hydraulic head and conductivity through geostatistical inversion 总被引：5，自引：2，他引：3
A. F.?Hernandez S. P.?NeumanEmail author A.?Guadagnini J.?Carrera 《Stochastic Environmental Research and Risk Assessment (SERRA)》2003,17(5):329-338
Nonlocal moment equations allow one to render deterministically optimum predictions of flow in randomly heterogeneous media and to assess predictive uncertainty conditional on measured values of medium properties. We present a geostatistical inverse algorithm for steady-state flow that makes it possible to further condition such predictions and assessments on measured values of hydraulic head (and/or flux). Our algorithm is based on recursive finite-element approximations of exact first and second conditional moment equations. Hydraulic conductivity is parameterized via universal kriging based on unknown values at pilot points and (optionally) measured values at other discrete locations. Optimum unbiased inverse estimates of natural log hydraulic conductivity, head and flux are obtained by minimizing a residual criterion using the Levenberg-Marquardt algorithm. We illustrate the method for superimposed mean uniform and convergent flows in a bounded two-dimensional domain. Our examples illustrate how conductivity and head data act separately or jointly to reduce parameter estimation errors and model predictive uncertainty.This work is supported in part by NSF/ITR Grant EAR-0110289. The first author was additionally supported by scholarships from CONACYT and Instituto de Investigaciones Electricas of Mexico. Additional support was provided by the European Commission under Contract EVK1-CT-1999-00041 (W-SAHaRA-Stochastic Analysis of Well Head Protection and Risk Assessment). 相似文献
8.
The evolution of pore-water and the composition of solid phases in the vadose zone of pyritic tailings was studied by means of unsaturated column experiments. Several columns of water-saturated mine tailings were dried during 125 days under controlled laboratory conditions. The columns were dismantled at four successive drying stages and the evolution of pore-water, mineralogy, water content and temperature was characterized.Sulfide and aluminosilicate minerals present in the waste dissolved, releasing sulfate and other solutes (mainly Fe, Zn, Cu, Al, Mg and Ca) to the pore-water. Evaporation caused a crust of efflorescent, water-soluble sulfates to develop over the complete top surface of the columns and into the pores of the underlying waste material. This crust, which has also been identified in the field, changed the hydraulic properties of the tailings and produced a decrease in the evaporation rate of the columns. Moreover, these water-soluble precipitates (mainly rozenite, szomolnokite, halotrichite, hexahydrite, mirabilite and gypsum) acted as temporary sinks for Cd, Pb, Co and Ni, which could be released to the surface run-off or the groundwaters during rainfall events under field conditions.Pore-water evolution was determined not only by geochemical processes (dissolution of sulfides and aluminosilicates, precipitation of secondary phases) but also by thermal and hydraulic processes. Progressive dilution was observed in the lower part of the columns. Dilution was caused by the thermally driven vapor flux from the top of the column to its colder bottom and subsequent condensation therein. This process, which may also occur in tailings under sub-arid climate, played a key role on the evolution of pore-water with increasing drying. 相似文献
9.
Komatiites are fascinating volcanic rocks. They are among the most ancient lavas of the Earth following the 3.8 Ga pillow basalts at Isua and they represent some of the oldest ultramafic magmatic rocks preserved in the Earth’s crust at 3.5 Ga. This fact, linked to their particular features (high magnesium content, high melting temperatures, low dynamic viscosities, etc.), has attracted the community of geoscientists since their discovery in the early sixties, who have tried to determine their origin and understand their meaning in the context of terrestrial mantle evolution. In addition, it has been proposed that komatiites are not restricted to our planet, but they could be found in other extraterrestrial settings in our Solar System (particularly on Mars and Io). It is important to note that komatiites may be extremely significant in the study of the origins and evolution of Life on Earth. They not only preserve essential geochemical clues of the interaction between the pristine Earth rocks and atmosphere, but also may have been potential suitable sites for biological processes to develop. Thus, besides reviewing the main geodynamic, petrological and geochemical characteristics of komatiites, this paper also aims to widen their investigation beyond the classical geological prospect, calling attention to them as attractive rocks for research in Planetology and Astrobiology. 相似文献